[PATCH 1/1] UBUNTU: SAUCE: arm64: dtbs: Add symbols when compiling dtb

[Paolo Pisati]

BugLink: http://bugs.launchpad.net/bugs/1782121

Overlay files are dtb fragments that, upon boot, patch the main dtb
board file to enable Raspberry Pi hardware extension (commonly known as
Raspberry HATs) to work.

This mechanism works fine for the bionic/raspi2 kernel, but it didn't
work for the raspi2 arm64 variant since our dtb files are missing
symbols there.

This patch instruct the device tree compiler to add symbols to the dtb
files during the 'make dtbs' target, and fix the overlay patching
mechanism for bionic/raspi2 arm64.

The resulting increase in size is negligible (~30kb for the whole kernel
package).

Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
---
 arch/arm64/boot/dts/broadcom/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/boot/dts/broadcom/Makefile b/arch/arm64/boot/dts/broadcom/Makefile
index 11180bba170b..217a0dc28ed8 100644
--- a/arch/arm64/boot/dts/broadcom/Makefile
+++ b/arch/arm64/boot/dts/broadcom/Makefile
@@ -4,5 +4,10 @@ dtb-$(CONFIG_ARCH_BCM2709) += bcm2710-rpi-3-b.dtb
 dtb-$(CONFIG_ARCH_BCM2835) += bcm2710-rpi-3-b.dtb
 dtb-$(CONFIG_ARCH_BCM2835) += bcm2710-rpi-3-b-plus.dtb
 
+# Enable fixups to support overlays on BCM2835 platforms
+ifeq ($(CONFIG_ARCH_BCM2835),y)
+	DTC_FLAGS ?= -@
+endif
+
 subdir-y	+= northstar2
 subdir-y	+= stingray
-- 
2.17.1